How do I find out what tool a shortcut is triggering?
In future, to find out what tool is being triggered by a shortcut, you can search in the 'Input' section of the 'User Preferences'.

Going to File> User Preferences (Ctrl+Alt+U)> Input, you can use the search field to search for tools assigned to shortcuts. The 'Filter Method' drop down box must also be set to 'Key-binding' for this to work: 



This will yield a list of all tools in blender using that shortcut. For example, "ctrl n" would result in showing that that shortcut will 'Make Normals Consistent' for meshes in edit mode. 'Make Normals Consistent' will make sure all faces of the mesh are facing the right way and shaded correctly see: Render has strange artifacts. It also lists other commands that use the same shortcut such as 'Reload Start-up File':



You can also look in the bottom of the toolbar (T) in the 3D view immediately after using the shortcut to see what was triggered: